Narrowing is arithmetic before it is art. Take a subject down the ladder one rung at a time, set the clock and the number of main points, and watch the seconds per point fall. A point needs about 65 seconds to be developed rather than mentioned — below that, watch which parts of it get cut first.
1 · Pick a subject
2 · Climb down the scope ladder
3 · The clock you were actually given
4 · How many main points you are planning
5 · Your speaking rate
110 · deliberate140 · typical170 · rushing
Intro & conclusionDeveloped (65s+)SqueezedHeadline only
When a speech runs long, cut the topic, not the evidence. Students instinctively delete examples, sources and explanations — the very material that makes a point convincing — and keep every heading. Delete a whole main point instead. Two well-supported points beat four asserted ones every time.